松島湾における溶存有機物質と鉄の空間分布及び季節変化

Abstract

In this study, we investigated the spatial and seasonal distributions of dissolved organic matter (DOM) and iron in Matsushima Bay, Japan from November 2003 to October 2004. The chemical characteristics of DOM, such as concentrations of dissolved organic carbon (DOC) and XAD resin absorbed organic carbon (XOC), UV absorbance, molecular weight and carbon stable isotope ratio, were also studied in the bay and the Takagi River. In the bay, DOC concentration increased particularly in summer. The XOC concentration and molecular weight of DOM decreased along the river to the bay. The carbon isotope ratio of DOM indicated that a significant amount of humic substance was produced in the bay. Dissolved iron concentration rapidly decreased with the increase in salinity from the river to the bay and was extremely low in seawater of high salinity. It was considered that this decrease in dissolved iron concentration was attributable to the precipitation of dissociated iron from organic compounds caused by the increase in the concentration of metal cations as river water meets seawater.